/**
     * Show the application dashboard.
     *
     * @return \Illuminate\Http\Response
     */
    public function index()
    {
        $completed_lessons_count =
            DB::table('lesson_user')->selectRaw('COUNT(lesson_id)')->whereIn('lesson_id', function ($query) {
                $query->select('id')->from('lessons')->whereIn('section_id', function ($query) {
                    $query->select('id')->from('sections')->whereRaw('`sections`.`course_id` = `courses`.`id`');
                });
            });

        $lessons_count = Lesson::selectRaw('COUNT(id)')->whereIn('section_id', function ($query) {
            $query->select('id')->from('sections')->whereRaw('`sections`.`course_id` = `courses`.`id`');
        });

        $last_completed_lesson_id = DB::table('lesson_user')->select('lesson_id')->whereIn('lesson_id', function ($query) {
            $query->select('id')->from('lessons')->whereIn('section_id', function ($query) {
                $query->select('id')->from('sections')->whereRaw('`sections`.`course_id` = `courses`.`id`');
            });
        })->orderBy('lesson_id', 'desk')->limit(1);

        $courses = auth()->user()->courses()
            ->select('*')
            ->selectSub($completed_lessons_count, 'completed_lessons_count')
            ->selectSub($lessons_count, 'lessons_count')
            ->selectSub($last_completed_lesson_id, 'last_completed_lesson_id')
            ->get();

        return view('home', ['courses' => $courses]);
    }